Aww i'll explain it again.
In your world editor, go to Layers -> Regions
Then put one region over the part of the map where you want the spawn to be.
In my maul it looks like this:

whether you want yellow to have creeps coming from ONE side.
If you want creeps coming from more than one sides, you have to make it 2 regions -> like this:

but remmber: unless you don't change the variable
Monster_Amount, there will be 20 units per region which are created at the start of a level (i suppose).
So if you want
ONE location for yellow with 40 creeps, put both regions next to each other. And don't forget to name them
To spawn the units, look under 'Core functions' (in triggers) for the trigger 'core function', it should look like this:

Unit Group - Create Monster_Amount Monster_Type for Player 12 at (Center of Left Spawn 2) <gen>
. Copy that and paste it under the triggers. Now change the (Center of Left Spawn 2 <gen> to your newly added regions.
And be sure to make them move to the waypoint you want them to move to. Therefore make a new trigger which puts them into a unitgroup and forces them to move to location x, as like

Events


Unit - A unit owned by Player 12 (Brown) enters *Your new region*

Conditions

Actions


Unit group - Pick every unit in *your region* owned by Player 12 and do Unit - Move (Picked unit) to location x
This trigger still leaks.
To remove the leak which is caused, you have to recreate the whole spawntrigger for ALL regions.
If you're interested in what it looks like, click the following thumbnail

.
Unless the trigger being in german, it basically creates 1 unit of the level's respective monnster type at the center of the different regions' centers and orders the created unit to move to the waypoint i want it to. The whole thing is wrapped in an Integer Loop which repeats the unitspawn upto the predefined Monster_Amount (20).
I hope it helps D: